This invention relates to the correlation of a two-dimensional input image with a two-dimensional reference image by illumination of a transmissive mask representing the reference image with an optical signal representing a portion of the input image.
Optical correlation systems are known that utilize a transmissive mask having a transmissivity pattern defining a reference image to be correlated with an image represented by an optical signal projected on the mask. Typically, both the input and reference images are in the form of a rectangular matrix of pixels (picture elements) and correlation is performed by setting up a row or column relationship between the input and reference image pixel arrays and then correlating on a row-by-row or column-by-column basis.
Since correlation in the conventional systems proceeds on a unidimensional basis (i.e. row-by-row or column-by-column) such systems perform only one-dimensional correlation, or two-dimensional correlation built upon the summation of plural one-dimensional correlations.
Clearly, an optical correlator capable of performing real-time, two-dimensional correlation of a pair of images in a single operation would represent an improvement over the prior art optical correlations by reducing the total number of operations presently required for two-dimensional correlation. In view of a reduction in the number of operations, it would be expected that such a device would require a smaller complement of hardware and fewer operational steps than the prior art optical correlators.